Cameron,
I totally understand your frustration.
Unfortunately, it might be very difficult or even impossible to recover a hacked account if the main email address (Username) have been changed. Hackers might change most of the information linked to the account, so the recovery form is the only option to recover your account. But the chances are less.
Account Recovery Form: https://account.live.com/acsr
Detailed steps on how to use the Account Recovery Form can be found here: https://support.microsoft.com/office/b19c02d1-a...
It's important to note that Microsoft Support will not be able to grant you access to your account, you will be sent back to the Account Recovery pages that have been linked above.
While it might not be the outcome you are looking for, if you’re unsuccessful in recovering your account, then you will need to create a new Microsoft account. You can do that by clicking this link: https://signup.live.com/
To avoid this instance from happening in future again, you could go through the guidelines below on how to help keep your Microsoft account safe and secure -
https://support.microsoft.com/help/628538c2-700...
Let me know if you need more help.
Regards,
Gunasekar N